It doesn’t take hours to make an intense, dark and rich French onion soup

Becky Krystal

THE WASHINGTON POST – Few soups get people as misty-eyed as French onion.

Sure, I count myself among the many who cry while slicing pounds and pounds of onions. (I hate to think how many people walked by the fishbowl window of The Washington Post Food Lab and wondered what was wrong with the woman weeping as if it was the opening few minutes of Up.) Despite the waterworks, it’s hard to resist the result: A rich, fragrant, deeply coloured pot of comfort.

The best renditions are so beautiful, they might bring a tear to your eye – at least metaphorically.

That’s the kind of recipe I’m presenting you with today. Even better, this Fast French Onion Soup from kitchen wizard and Serious Eats chief culinary adviser J Kenji López-Alt is speedier than a traditional preparation, and it doesn’t sacrifice flavour in the interest of time.

His method, which I culled from his impressive 2015 cookbook, The Food Lab, uses sugar, baking soda and increased heat to speed up the onion caramelisation process.

The sugar (only one tablespoon, don’t worry!) contributes sweeter, deeper, faster-developing flavour. Baking soda speeds up browning (that Maillard reaction you may have heard about) and leads to softer onions by breaking down the cells faster. And heat? Well, naturally, food cooks faster at a higher temperature, and the addition of water here reduces the risk of burning and better distributes all the sugars.

As the subtitle of the book says, “better home cooking through science.”

“If you’re willing to put in the work to make French onion soup the traditional way,” as in several hours, “it does develop different flavours,” López-Alt told me.

They’re not necessarily flavours that are better or worse than with the quicker approach.But will most people be able to tell the difference when this recipe takes only around half an hour to caramelise the onions? (If you’re as deliberate with a knife as I am, it might take you less time to caramelise than to slice the five pounds of them.)

Certainly not, and it might not even be discernible to a typical palate in a side-by-side tasting.

“They’re both good; they’re just a little different,” López-Alt says.

“Different” might not be the first word that comes to mind when you taste this soup. “Like velvet” was one taster’s observation, with the rest of the sentiments falling somewhere between “amazing” and “holy cow”. Speaking of cow … the deeply caramelised onions created such a rich, dark liquid that it prompted some to wonder whether the soup had been made with beef broth. Nope. I got stunning results using a good store-bought chicken broth.

And it wouldn’t be a huge leap to make this with a good vegetable broth if you prefer to keep things meatless. “The broth is very important,” López-Alt says, but that does not mean you have to abandon the prospect of French onion soup at home if you don’t have homemade broth. If you do, great. If not, I’m not sure you’d be able to tell the difference there, either, when the onions do so much of the work for you.

Cooking the onions at a higher temperature requires a bit more hands-on work, as you have to make sure you aren’t burning them or the flavourful browning on the bottom of the pan. The goal is to get everything as dark as possible without it turning black, López-Alt says. Medium-high is a relatively safe heat. Even then, you might have to make adjustments, depending on your pan and stove top. You also must be vigilant about stirring the onions every few minutes, which is another safeguard, with the water, against scorching. It’s how you achieve even, robust colour, as well.

The only way a whole pot of this oniony bliss gets any better is if you top each portion with toasted bread and a generous layer of cheese. Tears of joy? Fine by me.


Active: One hour five minutes | Total: One hour 20 minutes

Four to eight servings (makes about seven and a half cups)

Don’t mistake fast for flavourless in this classic, comforting soup. J Kenji López-Alt’s genius method uses sugar, baking soda and increased heat to speed up the onion caramelising process. The recipe gave us the richest-tasting soup of the several that we tested, with a liquid so dark and robust that it would be easy to think it was made with homemade beef broth rather than store-bought chicken broth.

If you don’t have broiler-safe bowls for serving, broil the slices of cheese-covered bread on a sheet pan before floating them on top of the soup.

Make Ahead: The soup can be refrigerated for up to one week or frozen, ideally flat in zip-top bags, for several months.


One tablespoon sugar

Five pounds yellow onions, thinly sliced

Two tablespoons unsalted butter

A quarter teaspoon baking soda

Two teaspoons kosher salt, plus more as needed

Half cup water

Six cups homemade or low-sodium chicken broth

Two bay leaves

Six to eight sprigs fresh thyme

Freshly ground black pepper

One baguette, sliced one-inch thick and toasted

Eight ounces Gruyère or Swiss cheese, grated


Pour the sugar into a large Dutch oven and cook over medium-high heat, swirling the pot gently as the sugar melts, until it is completely liquid and a golden-brown caramel.

Add the onions and cook, stirring with a wooden spoon and tossing constantly until they are evenly coated in the caramel, about 30 seconds.

Add the butter, baking soda and two teaspoons salt and cook, stirring occasionally, until the onions are a light golden brown and a brown coating has started to build up on the bottom of the pot, about 10 minutes.

Add two tablespoons water and scrape the browned coating from the bottom of the pot.

Shake the pot to distribute the onions evenly over the bottom and cook, shaking occasionally, until the liquid evaporates and the browned coating starts to build up again, about five minutes.

Add two more tablespoons water and repeat, allowing the coating to build up and scraping it off, then repeat two more times. (Reduce the heat as needed if the coating is burning and turning black.)

By this point, the onions should be deep brown.

If not, continue deglazing and stirring until the deep brown colour is reached.

Add chicken broth, bay leaves and thyme, bring to a boil, and reduce the heat to low, so the soup is at a gentle simmer. Simmer, uncovered, until the liquid is deeply flavoured and slightly reduced, about 15 minutes. Season to taste with salt and pepper. Discard the bay leaves and thyme.

To serve, heat the broiler. Ladle the soup into four broiler-proof bowls. Float one or two bread slices on top of each bowl and cover with the grated cheese.

Broil until the cheese is melted, bubbly and golden brown in spots. Serve immediately.